Typically, vehicle seat assemblies include a recliner mechanism which supports a substantially U-shaped seat back frame with a cross-member extending across the back frame, and head rest guide tubes extending through the back frame for supporting a head rest assembly. Normally, an aluminum back frame comprises a hollow aluminum tube bent into a U-shaped configuration. The tube is usually bent in an unheat-treated condition, and then heat-treated after bending, or alternatively, the tube is annealed locally for bending. The heat-treating operation adds substantial manufacturing, handling, and shipping costs to the assembly.
The prior art bent tubes are deformed in the upper bending corners and have thin walls in the attachment areas, which results in a high shear stress. The thin attachment areas require a splint or insert to be inserted therein to reduce the shear stress. Furthermore, for attachment of the head rest guide tubes, apertures must be bored through both sides of the back frame tube, which may be awkward and may unnecessarily increase manufacturing costs.
It is desirable to provide a seat assembly in which localized heat treatment is not required prior to bending the seat back frame, heat treatment after frame completion is not rigid, and in which structural integrity is enhanced and manufacturing costs are reduced.